This invention relates in general to preventing the production of particulate materials through a wellbore traversing an unconsolidated or loosely consolidated subterranean formation and, in particular, to a screen assembly and method for obtaining a substantially complete gravel pack within an interval of the wellbore.
Without limiting the scope of the present invention, its background is described with reference to the production of hydrocarbon fluids through a wellbore traversing an unconsolidated or loosely consolidated formation, as an example.
It is well known in the subterranean well drilling and completion art that particulate materials such as sand may be produced during the production of hydrocarbons from a well traversing an unconsolidated or loosely consolidated subterranean formation. Numerous problems may occur as a result of the production of such particulate. For example, the particulate cause abrasive wear to components within the well, such as tubing, pumps and valves. In addition, the particulate may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids by processing equipment at the surface.
One method for preventing the production of such particulate material to the surface is gravel packing the well adjacent to the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a sand control screen is lowered into the wellbore on a work string to a position proximate the desired production interval. A fluid slurry including a liquid carrier and a particulate material known as gravel is then pumped down the work string and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.
The liquid carrier either flows into the formation or returns to the surface by flowing through the sand control screen or both. In either case, the gravel is deposited around the sand control screen to form a gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the particulate carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of particulate materials from the formation.
It has been found, however, that a complete gravel pack of the desired production interval is difficult to achieve particularly in long or inclined/horizontal production intervals. These incomplete packs are commonly a result of the liquid carrier entering a permeable portion of the production interval causing the gravel to form a sand bridge in the annulus. Thereafter, the sand bridge prevents the slurry from flowing to the remainder of the annulus which, in turn, prevents the placement of sufficient gravel in the remainder of the annulus.
Prior art devices and methods have been developed which attempt to overcome this sand bridge problem. For example, attempts have been made to use devices having perforated shunt tubes or bypass conduits that extend along the length of the sand control screen to provide an alternate path for the fluid slurry around the sand bridge.
It has been found, however, that shunt tubes installed on the exterior of sand control screens are susceptible to damage during installation and may fail during a gravel packing operation. In addition, it has been found that on site assembly of a shunt tube system around a sand control screen is difficult and time consuming due to the large number of fluid connections required for typical production intervals. Further, it has been found that the effective screen area available for filtering out particulate from the production fluids is reduced when shunt tubes are installed on the exterior of a sand control screen.
Therefore a need has arisen for an apparatus and method for gravel packing a production interval traversed by a wellbore that overcomes the problems created by sand bridges. A need has also arisen for such an apparatus that is not susceptible to damage during installation and will not fail during a gravel packing operation. Additionally, a need has arisen for such an apparatus that is cost effective and does not require difficult or time consuming on site assembly. Further, a need has arisen for such an apparatus that does not require a reduction in the effective screen area available for filtering out particulate from the production fluids.
The present invention disclosed herein comprises a screen assembly and method for gravel packing a production interval of a wellbore that traverses an unconsolidated or loosely consolidated formation that overcomes the problems created by the development of a sand bridge between a sand control screen and the wellbore. Importantly, the screen assembly of the present invention is not susceptible to damage during installation or failure during the gravel packing operation, is cost effective to manufacture and does not require difficult or time consuming on site assembly. In addition, the screen assembly of the present invention allows for a relatively large effective screen area for filtering out particulate from the production fluids.
The sand control screen assembly of the present invention comprises a base pipe that has one or more perforated sections and one or more nonperforated sections. A plurality of ribs are circumferentially spaced around and axially extending along the exterior surface of the base pipe. Two of the ribs are positioned within each of the nonperforated sections of the base pipe. A screen wire is wrapped around the plurality of ribs forming a plurality of turns having gaps therebetween. A filler material is disposed within the portions of the gaps that are circumferentially aligned with the nonperforated sections of the base pipe.
The screen assembly includes one or more slurry passageways each of which are defined by one of the nonperforated section of the base pipe, the two ribs positioned within that nonperforated section of the base pipe and the portion of the wire and the filler material in the gaps that are circumferentially aligned with that nonperforated section of the base pipe. The slurry passageways are used to carry a fluid slurry containing gravel past any sand bridges that may form in the annulus surrounding the screen assembly. The fluid slurry is discharged from the screen assembly via a plurality of manifolds that are in fluid communication with the slurry passageways. The manifolds selectively discharge the fluid slurry to a plurality of levels of the interval through exit ports formed therein when the screen assembly is in an operable position. The exit ports may be either circumferentially aligned with the slurry passageways, circumferentially misaligned with the slurry passageways or both. The fluid communication between the manifolds and the slurry passageways may be established using tubes that extend from the manifolds into each adjacent sections of the slurry passageways.
In embodiments of the present invention wherein the screen assembly includes more than one section of sand control screen, each including a portion of the slurry passageway, the screen assembly includes a manifold between each of the sand control screen sections. These manifolds provide fluid communication between the portions of the slurry passageways of the adjacent sand control screen sections and deliver the fluid slurry into the interval surrounding the screen assembly.
In one embodiment of the present invention, the exit ports are created directly through the wire and the filler material in the gaps that are circumferentially aligned with the nonperforated sections of the base pipe instead of in manifolds. In this embodiment, tube segments may be disposed within the slurry passageways at the locations where the exit ports are created to provide support to the screen wire at these locations.
The method of the present invention includes traversing a formation with the wellbore, positioning a sand control screen assembly having one or more slurry passageways as described above, within the wellbore, injecting a fluid slurry containing gravel through the slurry passageways such that the fluid slurry exits the screen assembly through exit ports in manifolds or through the screen wire at a plurality of levels of the interval and terminating the injecting when the interval is substantially completely packed with the gravel.